Sight for antiaircraft machine guns



BB ZBEQ Jan. 22, 1935. J. NYBERG SIGHT FOR ANTIAIRCRAFT MACHINE GUNS Filed April 5. 1935 2 Sheets-Sheet l Jan. 22, 1935. J. NYBERG 1,938,934

SIGHT FOR ANTIAIRCRAFT MACHINE GUNS Filed April 5, 1933 2 Sheets-Sheet 2 m R Q WW-M W 15 T P L) Wham l .1. n '5 A M s atoms; Ri

ruwnlcu Jan. 22, 1935 UNITED STATES PATENT OFFICE Application April 5, 1933, Serial No. 664,672 In Sweden April 8, 1932 4 Claims. (Cl. 33-53) My present invention refers to a sight for antiaircraft machine guns which can be used either as front sight or as back sight.

On firing at targets moving in the air, for instance aeroplanes, it may be assumed that the target during the period of firing moves in one and the same plane, generally the horizontal plane, and at a constant speed.

In Fig. 1 the figure 1 designates an aeroplane, F the front sight of a gun and B its back sight. The line of sight going through E and F to 1 is designated by s. In order to hit the aeroplane the barrel of the gun must then be directed so that the projectiles will hit the aeroplane in a future position at P.

The time required for the aeroplane to move from the actual position 1 to the future position P should be equal to the time of flight of a bullet from the muzzle to P. The distance between 1 and P is in the following specification called the lead, which thus means the distance from the actual position at the firing to the future position where the aeroplane should be hit by the bullet.

It is the same thing with other aeroplanes occupying the positions indicated by 2, 3 and 4 and moving toward P. The locus for the lead distances is thus represented by a circle in the moving plane of the target, the center of which is P and whose radius is equal to ut, if u is the speed of the aeroplane and t the time of flight of the bullet to P. If the course of the bullet were straight and the speed of the same were constant the loci for different points of the trajectory of the bullet would be a conus with its point at the muzzle of the barrel. The sight (back or front sight) will therefore be a direct reduction of said locus-circle in a plane cutting the conus parallelly to the moving plane of the aeroplane.

It is previously known to use such a circle as anti-aircraft sight and. also to use in connection therewith separate means for changing the angle of projection, so that for every height-angle of the aeroplane (in relation to the horizontal I plane) and every angle of sight a desired lead distance is obtained. In previously known constructions the means for regulating said means have, however, for obtaining correct results, been very complicated and required several members of the gun crew, some of them having operated the vertical and others the lateral deflection corrections of the sight, and even others have operated the tangent elevation-mechanism. In the known sight systems said sight circle has also generally occupied a vertical position.

The sight system forming the object of the present invention and being substantially adapted to be used on machine guns is very simple and acts automatically so that only one man is required for managing the gun including its sight.

The characteristic feature of the invention consists in this that the measure of the lead distance is obtained by means of a sight-circle supported by a shaft located in a plane through the centre of the circle and at right angle to the axis of bore, said shaft being by mechanical means connected with a portion of the gun mount, which portion partakes in the sideways movements of the barrel in such a way that in every elevation position of the barrel the sight-circle is automatically held in a certain position parallel to the plane in which the target moves, for instance in a horizontal position.

The sight-circle ought to be placed at a distance below or above the axis of the shaft of the circle, depending on whether the sight-circle is used as front sight or as back sight. Said distance corresponds to the tangent elevation for a certain average firing distance, whereby the corresponding angle of projection is automatically altered with the angle of elevation.

The mechanical motion-transmitting devices, which connect the shaft of the sight-circle with that part of the gun mount partaking in the sideways movements of the barrel, preferably consist of two links articulated to one another so as to form a parallelogram coupling.

The invention is illustrated on the accompanying drawings. Fig. 1, mentioned above, schematically illustrates the principle of the invention. Fig. 2 is a side view of a machine gun provided with the present sight system, used as front sight. Fig. 2a is a front view. Fig. 3 shows the same as Fig. 2 with the exception that the sight-circle is used as back-sight. Figs. 47 show details.

In Figs. 2 and 3 the figure 6 designates the barrel of an anti-aircraft gun, 7 is its mount and 8 is an arm rotatable on said mount and carrying the barrel which is articulated to the same at 9 being the elevation centre. Articulated to the turnable support arm 8 is a link 10 which has its opposite end articulated to one end of an other link 11 which is in turn rigidly connected with one end of the shaft 12 on which the sightcirole 13 is supported.

As is seen from Fig. 4 the shaft 12 supporting the sight-circle 13 is not straight but is U-shaped in such a way that the portion 12a of the same on which the sight-circle is located is displaced at a distance u from the axis of the shaft 12.

This distance it indicates the tangent elevation. If the sight-circle is used as back-sight the shaft 12 is turned in such a way that the circle is located above the shaft 12 (Fig. 3), but if it is used as front sight the circle is located below the said shaft (Fig. 2).

The sight-circle 13 is supported in a ring 21 carried by a support 22 fixed on the barrel and the shaft 12 is acted upon by means of a frictional brake of the form illustrated in Figs. 6 and '7. The right-hand end of the shaft 12, Fig. 6, is supported in the bearing 100 carried by the ring 21 and is provided in its end with a conical recess 12a: in which is fitted the tapered extremity of a pin-like member 121 rigidly fixed to the link 11. The left end of the shaft 12 illustrated in detail in Fig. 7 is pointed and engaged in a correspondingly shaped recess in a spring-pressed bearing stud 102 slidably mounted in the bearing 103 carried by the ring 21. The bearing stud 102 is engaged by a spring 101 normally tending to press the shaft 12 to the right and maintaining the walls of the recess 12:: in tight frictional engagement with the pointed end of the pin 12y. The friction developed is sufficient to cause the shaft 12 to be turned with the link 11 when the latter is actuated but when sufiicient force is applied, the shaft 12 may be turned relatively to the link 11 and by this means the sight-circle can be given any desired starting position parallel with the course or moving plane of the target. Due to the link connection 10, 11, this position is then automatically maintained at all angles of elevation of the barrel. As it can generally be "assumed that the course of the target is horizontal the shaft 12 is generally turned so that the starting position of the sightcircle is horizontal. Due to the parallelogram principle the links 10 and 11 will then, irrespective of the elevation of the barrel, maintain the starting position of the sight circle whereby the desired values of the lead distance and of the tangent elevation are automatically obtained.

Instead of using only one circle 13 two or several concentric circles 13a etc. may be used as shown in Fig. 5. The outer circle 13 is then used for a higher speed of the target (for instance m. per second) and the next circle 13a for a lower speed (for instance 60 m/sec.).

Instead of using several concentric circles for determining the angle of lead, the same result can be obtained by making the circle movable on the barrel in the longitudinal direction of the optic axis of the sight system. The link 10 is then provided with corresponding fixing points so that the parallelogram principle is maintained.

In Fig. 3 the link 10 is not directly fixed to the arm 8 but to a link 20 rigidly connected with the arm 8. By fixing the link 20 in different positions the starting position of the circle 13 can be varied. In this case it is therefore not necessary to use a frictional brake in the shaft 12.

It is obvious that the details shown and described can be modified in several ways without departing from the principle of the present invention.

I claim:

1. Sight for antiaircraft machine guns, provided with a mount, a rotatable member on said mount and means for connecting said member with the barrel, so that the barrel can be elevated on said member, a sight circle, a shaft supporting said sight circle rotatably located in a plane through the centre of the circle and above and at right angle to the axis of the bore, said circle being parallel to but offset from the axis of rotation of said shaft a distance proportional to the speed of the target, and mechanical means connecting said shaft with said rotatable member to maintain said circle in positions parallel to itself and in a plane parallel to the plane in which the target moves for all firing positions of the gun.

2. Sight for antiaircraft machine guns, provided With a mount, a rotatable member on said mount rendering possible sideways movements of the barrel, and means for articulating said member to the barrel, a sight-circle, a shaft supporting said sight circle rotatably located in a plane through the centre of the circle and above and at right angle to the axis of the bore, said shaft being U-shaped so as to form a crank, the crank part of the U-shaped portion being offset from the shaft part of the same a distance proportional to the speed of the target and supporting said circle which is adapted to be turned on the same, so that said circle may be adjusted to a starting position parallel tothe plane in which the target moves, and means for connecting said shaft with said rotatable member supporting the barrel so as to maintain said circle in positions parallel to itself and in a plane parallel to the plane in which the target moves for all firing positions of the gun, said means consisting of a link system arranged according to the parallelogram principle.

3. Sight for antiaircraft machine guns according to claim 1, characterized by the fact that the sight-circle is located in a ring carried by a support which is fixed on the barrel or on a part connected therewith.

4. Sight for antiaircraft machine guns as claimed in claim 2 characterized by the provision of a frictional brake in the connection between the shaft and the link system, whereby the shaft can be turned independently of the link system for placing the sight-circle in any desired starting position which is then maintained for all firing positions of the gun.

JOHANNES NYBERG. 

